The little, ever-growing biotech is all grown up. Look no further than Celgene's (Nasdaq: CELG) announcement yesterday that it was selling $1.25 billion in bonds.

Celgene's press release contained a laundry list of potential uses for its new-found cash, but one -- strategic transactions -- sticks out the most. Celgene's approved drugs are maturing, and while it does have some drugs in the pipeline, there's always room for more. An acquisition or licensing deal is the easiest way to get that done.

The company blew most of its dry powder when it agreed to purchase Abraxis BioScience (Nasdaq: ABII) for $2.9 billion in June. It looks like Celgene made the bond offering to replenish its cash coffers. And at today's rates, why not?

Celgene has grown revenue by 46% annually over the past five years, and if you held shares for the past five years, you'd have a nice double on your hands. Not too shabby, considering the broader markets are just about flat over that time frame. That's the power of biotech for you.

But don't expect the next five years to necessarily produce the same growth on the top line; that would result in a company with revenue the size of Bristol-Myers Squibb (NYSE: BMY) or Eli Lilly (NYSE: LLY). It's hard for drugmakers to keep up the steam; Bristol-Myers and Eli Lilly took decades to get where they are.

The problem is that every time you add a new drug, the next one has a smaller effect on the revenue. With Celgene's revenue now more than $3 billion per year, it'll take a blockbuster -- or a few smaller-selling drugs -- to move the revenue needle at the levels we've seen.

If you want hyper growth, you'll have to stick with development-stage drugmakers such as Exelixis (Nasdaq: EXEL), Seattle Genetics (Nasdaq: SGEN), or Array BioPharma (Nasdaq: ARRY). With multiple shots on goal, the companies can go from zero to 60 a lot faster than Celgene can go from 60 to 3,600.

That isn't to say there isn't a place for Celgene in your portfolio; you'll just need to move the company from the risky-hyper-growth category to the more-stable-but-slower-growth category.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool owns shares of Exelixis and has a disclosure policy.